Gestating sows prefer concentrate diets to high-fibre diet in two-choice tests

The supply of dietary fibre during gestation has been shown to improve the welfare of sows by reducing the expression of stereotypies that are commonly associated with a high feeding motivation in restricted-fed sows. The supply of preferred feeds can also contribute to the satisfaction of behavioural needs. The feed preferences of gestating sows were investigated in sixteen Large White × Landrace nulliparous sows, when offered feeds of different fibre and protein contents in two-choice preference tests carried out between their 8th to 13th weeks of gestation. During gestation, sows were fed 2.5 kg/d of a standard diet containing, in percentage of dry matter, 5.1% crude fibre (CF) and 15.8% crude protein (CP). The feed supply was limited to 2 kg on the day of the preference tests. Three days a week, sows were individually moved to a test arena, where they received three experimental diets presented in pairs (C–F, C–L and F–L): a control gestation diet (diet C, 3.3% CF, 16.8% CP), a high-fibre gestation diet (diet F, 9.3% CF, 16.8% CP), and a standard lactation diet (diet L, 3.8% CF, 20.3% CP). During each test sows were allowed to eat during 5 min, and the amount of each diet consumed, the first trough visited and the number of trough changes were recorded. Sows showed a marked preference for the diets C (P < 0.001) and L (P < 0.001) compared to the diet F, but did not display any significant preference between the diets C and L. There was an effect of the pair (P < 0.001): diets C and L were preferred when they were presented with the diet F, but they were similarly consumed when presented together. Most of the sows were lateralised, the left trough being more frequently visited first than the right one (P < 0.05). Trough changes presented a three-threshold pattern: changes were more frequent during the first minute of the test, then they decreased strongly a first time on the second minute (P < 0.001), and a second time on the fourth minute (P < 0.001). This study pointed out behavioural strategies exhibited by the sows in a two-choice test where fibrous diet was avoided by sows in the short-term compared to concentrate diets.